The senator's 32-year-old son, Adam Skelos, is also a focus of the investigation, sources familiar with the probe said. He was hired by an Arizona-based stormwater treatment company, AbTech, which was awarded a contract in his father's district despite the fact it wasn't the low bidder, the New York Times first reported.

U.S. Attorney Preet Bharara is also looking at Skelos' ties to the real estate industry, among other areas of inquiry, sources said. A spokesman for Bharara and an FBI spokesman declined comment.